ABSTRACT Parkinson's disease (PD) is among the most common forms of neurodegenerative disease in older adults. PD is associated with progressive loss of dopamine-producing neurons of the basal ganglia, which in turn disrupts normal basal ganglia activity and produces well-known movement abnormalities (e.g., bradykinesia, tremor). Of increasing concern are the effects of PD and its treatment on specific cognitive processes. Several contemporary neurocognitive models suggest that frontal-basal ganglia circuits play a central role in executive cognitive control. In our constantly changing environments, one particularly important aspect of executive control supported by this circuitry is the inhibition of behavior. Preliminary behavioral data for this application show that PD patients are less effective at inhibiting responses than healthy controls across several experimental paradigms. This data supports the central hypothesis behind this project that PD compromises the neurocognitive control system that is responsible for the inhibition of behavior. Specific aims provide additional empirical tests of this hypothesis by linking the response inhibition deficits in PD to underlying neurophysiological mechanisms and determining the effects of treatments (dopamine medication, subthalamic nucleus deep brain stimulation) for PD on behavioral and neurophysiological measures of inhibition. Career development training focuses on the acquisition of expertise in event-related brain potential (ERP) and electromyography (EMG) recordings that can be used to track the activation of an incorrect response and the inhibition of this response with millisecond precision as these processes unfold over the course of a mental reaction. Career development training and support is enhanced by local and outside collaborations that provide expert backgrounds in the neuroscience of cognitive control, the diagnosis and treatment of Parkinson's disease, and clinical neurophysiology. Cognitive deficits that accompany PD produce significant declines in quality of life and functional independence. A better understanding of these deficits and their neurophysiological mechanisms can lead to better treatments.